1. Field of the Invention
The present invention generally relates to an active device array substrate, and more particularly, to an active device array substrate for liquid crystal displays (LCDs).
2. Description of Related Art
The rapid development of the multimedia technology in modern age is largely attributed to the progress in the semiconductor devices and display apparatuses. In terms of displays, an LCD has played a major role in the mainstream display market due to advantages of high display quality, high space utilization, low power consumption and no radiation.
A thin film transistor liquid crystal display module (TFT-LCD module) mainly comprises an LCD panel and a backlight module, wherein the LCD panel usually comprises a TFT array substrate, a color filter substrate and a liquid crystal layer disposed between the above-mentioned two substrates, while the backlight module is for providing a planar light source required by the LCD panel to enable the LCD module to display.
A TFT array substrate can be divided into a display region and a peripheral circuit region, wherein a plurality of pixel elements arranged in an array on the display region and each pixel element includes a TFT and a pixel electrode electrically connected to the TFT. In addition, a plurality of scan lines and a plurality of data lines are disposed on the peripheral circuit region and the display region, wherein the TFT of each pixel element is controlled by the corresponding scan line and data line.
Whenever completing a process of TFT array substrate, an electric testing is usually conducted on the pixel elements on the TFT array substrate to decide whether the pixel elements can properly work or not. When a pixel element is found out of order, a repair process would be started on the defected device (for example, a defected TFT or a defected pixel electrode) or the circuit.
Usually a probe is used to perform an electric testing on the peripheral circuit. In more detail, the peripheral circuit is equipped with a plurality of testing pads electrically connected to the scan lines and data lines. During testing, the probe contacts each testing pad and produces a testing signal, according to which the pixel element can be decided for order or disorder. In order to increase the testing efficiency, a probe testing apparatus based on 6-probes testing architecture was developed by Photon Dynamics Inc. (PDI). When a probe testing apparatus of the PDI is used to test a panel having chip on glass (COG) design, only six testing lines are used for connecting the TFT array to a detecting circuit. Therefore, once an electrostatic discharge (ESD) occurs, except for an inner shorting ring, there is no other transmission paths for releasing the static charges, which likely causes a damage on the circuit.